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Unformatted text preview: 1 Exercise 39: Phylum Arthropoda • Most diverse and most abundant phylum of animals -- range from 2 to 10 million species. • arthro = jointed, poda = foot or appendage • Adaptive advantages – Exoskeloton – external skeleton is made of chitin, provides protection, a moisture barrier, and a place for muscle attachment, limit growth (periodically shed exoskeleton and enlarge body before new exoskeleton harden) – Jointed appendages – extension of main body, are adapted for locomotion, feeding, reproduction, defense, and sensing the environment. • Arthropods are coelomate with open circulatory systems and well-developed organ systems. Phylum Arthropoda • Bodies of arthropods are segmented. • Each body segment in ancestral arthropods had a single pair of appendages. • Extensive variation and elaboration of appendages in modern arthropods. – Covered by rigid exoskeleton and have flexible joints – Provide strength and flexibility • Arthropods have a hemocoel (“blood-hollow”) that provides space for internal organs and fluid circulation. • Subphylum Chelicerata : chelicerates (horseshoe crabs, spiders, scorpions, ticks, mites, etc) • Subphylum Crustacea : crustaceans (crabs, shrimps, crayfishes) • Subphylum Uriramia – centipedes, millipedes, and insects 2 Subphylum Chelicerata • Most anterior appendage modified into feeding structure – chelicerae (pincers or fangs) . • Second pairs of appendages modified for capturing prey, sensing environment, or copulating – pedipalps • Body segments of chelicerates are fused into two body regions: – Cephalothorax consisting of a fused head and thoracic segments – Abdomen is the most posterior body region. • Chelicerates lack antennae. Subphylum Chelicerata- Class Merostomata (horseshoe crabs) • Limulus are ancient marine chelicerates existing 500 mya....
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